The installation of electrical wiring in building construction is subject to stringently enforced codes in order to assure safe, trouble free operation. Wiring must be run in protective conduit with all of the connections made in junction boxes that provide both protection and access. Both the conduit and the boxes must be mounted to structural supports and constrained in accordance with the Electrical Code. In the typical commercial building, air ducts and wiring are installed overhead and subsequently concealed by a suspended ceiling. The junction boxes and conduit are placed at an elevation which allows room for ceiling segments to be lifted up and removed from their hanging framework to provide access for future maintenance. The electrical installation is supported in much the same manner as the suspended ceiling, by hangers anchored in the steel or concrete of the floor above. The National Electrical Code requires conduit to be supported within 36" of each entry to a junction box (18" for flexible conduit).
Others have disclosed wiring support arrangements which attach to the suspended ceiling frame. Such support however, requires that the electrical installation be made after the ceiling framework is in place, which is awkward and time consuming. The accepted method of support in the industry is to mount the junction box in place with one hanger and set a separate hanger within 36" for each conduit entering the box. An alternative method to setting separate hangers for each conduit is to bolt outwardly extending brackets on the box, above the entry holes, for clamp attachments. The brackets are made from cut lengths of formed "C" section structural members, with the open side facing down to receive clip washers for making a bolted connection to the back of the box. The conduit is supported by a clamp which is attached to the conduit and bolted to the underside of each bracket with another clip washer and bolt. The latter method eliminates a number of anchors and hangers and, inasmuch as the installer can pre-assemble the brackets to the box at floor level in a relatively short time, the overall cost of installation is reduced. Even so, there is a significant amount of time involved in assembly of the component parts, as well as the cost of the material.
The object of the present invention is to provide a simplified method and apparatus for supporting junction boxes and entering conduit so as to reduce labor and material costs for installation. A second object is to provide such method and apparatus for installation independent of suspended ceiling structure and in accordance with the specifications of the National Electrical Code.
The present invention accomplishes the above objects with a mounting bracket to which the back of any standard junction box can be bolted so as to provide conduit clamp attachments for all entry configurations without any need for field modification.